The invention relates to the field of motor vehicle drivetrains and in particular to the field of drivetrains having a main engine, an auxiliary engine and a parallel shaft transmission.
In this field, patent application WO 2005/065 976 (EATON CORPORATION) has described a transmission comprising a solid primary shaft and a hollow primary shaft which are coaxial and connected to a first engine by a double clutch. The hollow primary shaft comprises splines rotationally driven by a rotor belonging to a second engine. The transmission ratios are established by dog-clutch synchromeshes. The sequences for shifting from one transmission ratio to the next involve two steps. A first step in which the dog-clutch synchromesh of the next transmission ratio is engaged, then a second step in which the engine torque is switched from one primary shaft to the other primary shaft. This allows the shift to be performed under torque. In a transmission such as this, the size of the second engine is combined with the length of the transmission. The reverse-gear, second-gear and fourth-gear ratios are activated by the solid primary shaft. When one of these ratios is engaged, an additional clutch allows the second engine to be connected to the first engine. The additional clutch is of a size which further increases the length of the transmission.